1. Field of the invention
The present invention concerns a device for sensing the rotation speed of a bearing and a vehicle wheel hub assembly equipped with a device of this kind for measuring the rotation speed of the wheel.
2. Description of the Prior Art
It is known to equip vehicle wheel hub assemblies with rotation speed sensing devices which usually include an encoder member fastened to a rotating part of the hub assembly and a sensor fastened to a fixed part of the hub assembly and facing the encoder member with a particular airgap between them. The sensor senses the rotation speed of the encoder member to derive the rotation speed of the rotating part carrying the encoder member. In most devices currently used the sensor is often fastened to a fixed part of the bearing in a manner that is virtually irreversible, which can cause technical problems if it is necessary to change the sensor.
To overcome this problem French patent 2 659 450 (SKF) proposes a hub assembly device fitted with a removable sensor for a non-driven vehicle wheel hub assembly. These devices have the drawback that they can be used only with a specially designed stub axle which has a passage for centring the sensor support and through which the sensor support connection passes. The need for a specially designed stub axle may increase the cost of manufacture which is undesirable in the manufacture of automobiles.
An object of the present invention is to overcome this problem by proposing a device for sensing the rotation speed of a bearing with a demountable sensor assembly that is of simple shape, economic, of compact size in the axial direction and easy to mount on the bearing and to demount from said bearing if necessary.
Another object of the invention is a vehicle wheel hub assembly equipped with a device of this kind having a compact demountable sensor.
An important advantage of the invention is that it enables the use of a common basic bearing and surrounding parts structure in applications with and without a speed sensor which is particularly beneficial in connection with standardization of production by the bearing manufacturer and by the automobile manufacturer.